The present invention relates to a gun barrel base ring including an angular obturating ring mounted in a recess and means disposed between the base ring and the gun barrel for adjusting the axial play existing between the obturating ring and a breechblock.
A base ring of this type is disclosed in German Patent No. 1,578,046.A1, with particular reference to FIG. 1 thereof. According to this patent, manufacturing tolerances, particularly of the base ring, the wedge-type breechblock and an insert disposed in the breechblock, are compensated in that means are provided for adjusting the play between the base ring and the gun barrel as needed for the transverse movement of the breechblock. These means comprise twelve spacer rings of different thicknesses which are expensive to manufacture. Depending on the existing manufacturing tolerance, one of these twelve spacer rings is employed while the other eleven rings must be kept in storage near the gun. They are required, for example, for exchange if the base ring or the breechblock insert exhibits wear. It is therefore necessary to constantly check the supply of spacer rings at the gun and, moreover, they require much space in a storage depot.